Preparation Of A Composite Photocatalyst Based On Aloe Emodin And Its Applications In The Degradation Of Pharmaceutical Pollutants

With the rapid development of the pharmaceutical industry,drugs accumulate continuously in water bodies,and the problem of drug pollution in water bodies is increasingly serious.Therefore,it is urgent to develop an efficient,green and sustainable method to achieve the efficient removal of drug pollutants.Photocatalytic degradation technology uses visible light as energy to produce a variety of reactive oxygen intermediates to achieve green removal of drugs.Photocatalyst is the core of photocatalytic degradation technology,so the design and driving of new photocatalysts have become the focus of current research.In this paper,based on previous studies,composite photocatalyst AE/PMMA was prepared using natural organic photosensitizer aloe-emodin(AE)as photocatalyst and porous,strong adsorption,large specific surface area of polymethyl acrylate resin(PMMA)as the supporting material.The composite photocatalyst AE/PMMA was applied to the photocatalytic degradation of ofloxacin,chloramphenicol and diclofenac sodium.After Stirring in the dark for 0.5h and light for2 h.Ofloxacin was almost completely removed,and the biotoxicity of the degradation products almost completely disappeared.Meanwhile,the removal rates of chloramphenicol and diclofenac sodium were 84.0% and 97.0%,respectively,showing high photocatalytic activity.The strategy of designing composite photocatalysts based on natural products provides a feasible new way to solve the problem of drug contamination.The main research contents are as follows:1.Preparation and characterization of novel composite photocatalyst AE/PMMAComposite photocatalyst AE/PMMA-X containing different aloe emodin loading was prepared under mild conditions by combining the photosensitivity of AE and the excellent adsorption capacity of PMMA.The chemical structure of AE/PMMA-x was analyzed by X-ray diffraction(XRD)and Fourier infrared spectroscopy(FT-IR),and the successful preparation of AE/PMMA-x was confirmed by fluorescence inverted microscopy(FIM)and X-ray photoelectron spectroscopy(XPS).Specific surface area analysis(BET)was used to study the surface state of AE/PMMA-x,and field emission scanning electron microscope(FE-SEM)and transmission electron microscope(TEM)were used to analyze its morphological characteristics.The photophysical and electrochemical properties of AE/PMMA-x were investigated by UV-vis diffuse reflection(UV-vis DRS),transient photocurrent and electrochemical impedance spectroscopy,and the ability of photogenerated electron transport in AE/ PMMA-X was confirmed.2.Application of composite photocatalyst AE/PMMA in photocatalytic degradation of ofloxacinTaking ofloxacin(OFL)as the object,AE/PMMA-4 was applied to photocatalytic degradation of OFL,and the photocatalytic activity,recovery,stability and practical application of AE/PMMA-4 were studied.The optimum degradation conditions of ofloxacin were confirmed by optimizing the type of photocatalyst,the initial concentration of pollutants,the amount of photocatalyst and the initial p H value of solution.Using 40 mg AE/PMMA-4 as photocatalyst and 32 W fluorescent lamp(CFL)as light source for 120 minutes,the removal efficiency of 99.9% ofloxacin was achieved.At the same time,the photocatalytic system has good stability and recyclability,and can still maintain the degradation effect after three times of recycling.In addition,experiments were carried out in simulated urban wastewater and amplification experiments under sunlight to confirm the practical application value of the photocatalytic system.Finally,based on the study of degradation mechanism,total organic carbon(TOC)detection and the confirmation of degradation product structures,the path of AE/PMMA-4 photocatalytic degradation of OFL was studied,and the significance of this photocatalytic system was further confirmed through toxicity analysis.3.Application of composite photocatalyst AE/PMMA in photocatalytic degradation of multiple drugsIn view of the good photocatalytic activity of complex photocatalyst AE/PMMA-4 and the widespread existence of chloramphenicol(CAP)and diclofenac(DCF)in water,the application range of complex photocatalyst AE/PMMA-4 was further expanded,and it was applied to the photocatalytic degradation of CAP and DCF.The optimum degradation conditions were obtained by optimizing the initial concentration of solution.The practical application possibility of composite photocatalyst AE/PMMA-4 was further studied by simulated wastewater degradation experiment,solar energy degradation experiment and mixed drug system degradation experiment of OFL,CAP and DCF.In addition,LC-MS was used to analyze the photocatalytic degradation intermediates of CAP and DCF,and based on the previous mechanism analysis,the photocatalytic pathways of CAP and DCF were proposed.